Outer coating on 10BP4 peeling
 

The outer coating on my 10BP4 is peeling away. I have not gotten far enough along in the restoration to power up yet. Is this peeling an issue? What could I re-coat with?
Thanks,
Bill B.

Not an issue, it is a conductive coating mostly of graphite in an emulsion.
The coating is for the capacitance filtering of the HV.
If it bothers you so much, you can use a paint that has lots of aluminum in it.
Like rustoleum aluminum paint. follow safe procedures when using flamible paint.

That's a suggestion I hadn't heard before. I don't see why it wouldn't work. You can buy a special spray paint for this but it's expensive.

Thanks guys. I'll go with the alum paint. I kinda figured the coating was conductive since the tube sits on copper grounding strips mounted on the chassis.
Bill B.

In my experience the external dag (deflocculated Acheson graphite) coating on the kine needs to be present and grounded in many television sets, as electrostatic radiation of horizontal sweep signals can raise havoc with other circuitry, causing sync instability, undesireable images on the screen, etc. But in some sets I found that it didn't seem to matter much that the coating had all flaked away. I suppose that the "doorknob" capacitor found in the doghouses of most sets would sufficiently filter any such trash, but I guess not in some cases....

The conductive coating used to be available through General Cement--in both aerosol and brush-on forms, IIRC. Not sure where one would get the stuff now.... :dunno:

They used to make an aquadag spray can... Not sure if they still do, but that's what I'd go for if available. I bet Hawkeye has a contact for aquadag, but that would be for use in a spray gun.

Charles

I've stopped loose aquadag from falling off just by brushing water over the tube and letting it dry. It's water based, so wetting it seems to cause it to re-adhere to the glass.

Ayep! Yes indeed!

But you have to get it before the pieces are entirely lost. AMHIK.

But if you are going to be a scrub nurse for a kinescope you'd best have a jumper between the anode connection and what is left of the outer coating. :thmbsp:

Otherwise at least post vids of your activities, discoveries and resultant observations. :D

Edit; Soapbox time here: There is never any such thing as a fully-discharged kine!!!! Read this and heed it if you will. Glass can retain residual charges through a process of adsorption. Thus a successfully-discharged CRT can sometimes self-recharge to bite you when you thought it was finally laid to peace in the emf department.

I used to blame this phenomenom on my own forgetfulness.

The latest that shares this info I have is http://www.repairfaq.org/sam/crtfaq.htm

Read it as you may FYI--be such as it is. It at least tells me that God or Fate is not out to kill me whenever I handle an old kine.

Like firearms the CRT should never be assumed--or even mildly considered--an "unloaded" device.

Here's a product (Slip-Plate) that fills the bill and the price is right. The last can I bought, 12 oz. aerosol, cost $6.28 - purchased two years ago, at W. W. Grainger (Grainger's) in South San Francisco. They have 425 branches in the U.S. so there should be one near you.

The basic ingredient is graphite in acetone and petroleum solvents.

This is from the label: "Graphite is electrically conductive and may cause short circuits or other electrical malfunctions." Perfect!

I've heard that the bulk of the customers for this product are farmers who spray it on surfaces that typically gum up on harvesting equipment.

With careful removal of the old dag and appropriate masking of your tube and careful application it will come out looking factory fresh. I use a paper towel cardboard over the neck and cut a nice circle of Contact paper over the anode socket to closely duplicate the original dag coverage.

Roger

BTW, the Slip-Plate can describes the finish color as "dark gray." Trust me, it's the same color as the finish they put on at the tube factory.

Roger

Interesting! Is that really a paint-like product in that it will adhere to surfaces without rubbing off easily? The graphite sprays that I've seen are basically powdered graphite suspended in a 'carrier' solution that evaporates. ...Which is great for lubricating small mechanisms, but if you were to just spray it on a large flat surface like the outside of a CRT, the graphite would probably rub off at the slightest touch, and end up everywhere.

Excellent question Whirled One. The answer is that it is definitely in the "paint" category. It's not a can of Pledge. The solvents evaporate and it leaves a very nice coating which I find virtually indistinguishable from the original. I just presume that others have had the same experience I have had with old RCA's roundies shedding their Aquadag like autumn leaves. Perhaps RCA had a prepping problem.

Roger

Since I was not in a rush, I placed an order with Grainger's and got the Slip Plate. With shipping and sales tax, it came to just over $12. I scrubbed the 10BP4, removing all the loose stuff. The Slip Plate went on easily, just like paint, and I can't see any difference at all from the original coating. I have not not yet put my set back together, but this old roundie looks like it just came from the factory. Thanks for the suggestions.
Bill B.